Use Smaller P235/P60R18 Instead of P245/60R18 2007 Ford Edge

[mikulskn]

I bought a 2007 Ford Edge SEL Plus AWD with 200k miles (I am now fourth owner).  It now needs new tires and I plan to keep the vehicle for a few more years (as long as it keeps going).  I might put on 3k miles per year.  It has P245/60R18 stock size tires on it now with what appears to be the stock rims.  I have four used P235/60R18 Cooper Discover SRX tires from a previously vehicle with probably 25k miles left on them.  I do not know rim width of existing rims.  Can I put these used P235/60R18 size tires on the existing rims?  Besides the speedometer difference, is there any fitment, rim width, safety, driveability, etc concerns that I should not put these size/smaller tires on?   I couldn't find much out there on going "down in tire size" on the Edge, so any input would be appreciated.  Thanks.

[enigma-2]

You can do it, but there are a couple of considerations.

 

1) The most important is the load carrying capacity of the smaller tire. You're dealing with a heavy CUV and don't want to use a tire that's under the rating shown on the placard. 

 

Make certain the smaller tire has at least that same load index and speed rating as the OEM as shown on the label on the door B- Pillar.

 

2) Your speedometer will be off 1 mph at 60 mph.

 

Comparing the two sizes;

                     245    235

Dia:             29.6"   29.1"  (-1.7%)

Width:          9.6"    9.3"    (-3.1%)

Revs/mile: 682.    693.    (+11)

 

One other consideration is whether to have an alignment.  I don't know if the different (smaller) tire would change the geometry of the suspension enough to justify the cost of alignment. For me, I do it whenever I put on new tires. But I ~don't think~ it would be necessary with these. May wish to talk to the shop when the put them on. (If it's been awhile, or, if you just don't know, would probably be best to have it done. 

 

My local Ford dealer has installed new equipment when you pull your car into the service area. It checks every car's alignment and displays it on a flat screen monitor for you to see. If its off, they "recommend" an alignment. (Interesting enough, nearly 60% of the cars coming if for service need alignment. And the one ahead of me was really bad.

Edited July 23, 2021 by enigma-2

[mikulskn]

Good point on the alignment.  I never thought about it, but I guess a smaller tire can change the geometry of the suspension components, like the camber could be different because the tire would be sitting slightly lower.  I will have to get the alignment since it probably needs one anyway.

 

Since I would be putting used Cooper Discover SRX P235 tires on instead of buying new Discover SRX P245 tires, I looked up the Cooper SRX specs online of both tires and compared.  See attached.

Looks like the P235 tire actually has a higher load rating.  I wonder why.

 

Looking at rim width on the attached specs, seems the P235 tire also allows a wider rim width (as compared as if I would be putting the SRX P245 tire).  Seems strange too.

 

Looks like speed rating is higher on the 235 as well per attached pic, "V" versus "H" on the 245.  Go figure.

 

Thanks for input!

srx.pdf